The present invention relates to an IP telecommunication system, a method for controlling communication in an IP network, a client terminal and a client server, and more particularly, relates to a system wherein a client terminal applied to a thin client system may be used as, for example, an IP phone or a TV phone, and a telecommunication terminal, a telecommunication method and the like.
In recent years, due to the trend of price reduction in personal computers (PCs) and network devices, companies that promote streamlining of their operations by distributing terminals such as PCs to most of their employees have become a majority. As PC prices become lower and PC usage grows, the amount of maintenance work to be performed by intra-firm device administrators increases in proportion to the number of PCs. Examples of such maintenance work include version upgrading and bugfixing of operating systems (OSs) and business applications, responding to hardware-related failures, taking measures and countermeasures against computer viruses and the like. Performing such maintenance work requires significant management costs that will increase dramatically as the numbers of employees increase.
A method of system operation called the server-client method is employed as an approach for reducing such management costs. This method involves accumulating primary programs and data at a server side for collective management, and accessing the programs and data through remote control from the PC terminals of individuals. Terminals under the server-client method are ordinary PC terminals implemented with remote control programs. However, a PC terminal using this method is not required to accumulate application programs or data other than the remote control program. This allows thin client (hereinafter referred to as TC) terminals that are not equipped with storage devices such as hard disk devices to be used as terminals under the server-client method. In light of the recent enforcement of the personal information protection law, TC terminals have been attracting attention as terminals free from personal information leakage, and as a result a server-client method using such TC terminals has been gaining popularity.
FIG. 7 is a diagram showing a TC system employing TC terminals. The TC system comprises a TC server and a plurality of TC terminals. The TC server performs processing by having processes activated by each user communicate with the TC terminals to which they correspond one-to-one. Since each TC terminal does not store communication data in external storage devices such as fixed magnetic disk devices, their primary components are input/output devices and their driver/processing sections (so-called drivers), and data communication sections. Data processing of the main body desired by a user is performed at the TC server side. Therefore, it is no longer necessary to perform updating and the like of application programs at the TC terminals. This results not only in a reduction in terminal management costs, but also in prevention of information leaking even in the event of loss or theft of TC terminals since no confidential data is retained in the TC terminals.
On the other hand, in recent years, IP phones have been rapidly spreading. For example, a basic configuration of a corporate IP phone system is shown in FIG. 8. In FIG. 8, a single telephony server or a plurality of telephony servers carry out the role of a so-called internal phone exchange device, and perform call control between telephone terminals. Telephone terminals include an IP phone 801 that connects to an IP network, or a softphone 812 that is a telephone program on a PC. The softphone is a program that controls calling and receiving operations, generally using the PC that it is running on as its own telephone terminal. In addition, by comprising an image transmitting/receiving function that uses a camera 813 as a part of the softphone's function, the softphone can also be used as a TV phone terminal or a TV conference terminal. Communication with a fixed-line telephone 831 may be achieved via a fixed telephone network 830 through a gateway device 820, while communication with a cellular phone 833 may be achieved via a cellular phone network 832.
Next, fundamental operations of an IP phone will be described using an example wherein a telephone terminal 801 dials out to a softphone 812. When dialing out from the telephone terminal 801, a telephony server 800 receives this as a callout information from the telephone terminal. After confirming the telephone status and the like of the softphone 812, the telephony server notifies the telephone terminal 801 of an IP address 843 of the softphone, and notifies the softphone 812 of an IP address 842 of the telephone terminal. Then, both telephone terminals establish connection by mutually transmitting/receiving voice packets between their IP addresses, and achieve voice communication. Image communication can be achieved through a similar connection method, wherein connection is established by mutually transmitting/receiving image packets between softphones equipped with image functions.
Several technical challenges exist when realizing IP phone functions with a TC terminal according to the above described TC system. With a TC terminal, since application programs are executed at the TC server side, the TC terminal side cannot communicate even when a softphone that is a telephone program is executed on the TC server side. Even if the communication is established, the plurality of softphones virtually running on the TC server remains as a problem, preventing identification of virtual terminals on the TC server through call control under conventional IP address exchange methods. One such call connection method is provided, for example, in JP-A-2003-158534. More specifically, JP-A-2003-158534 presents a method of solving the problem wherein TC terminals cannot be identified from the outside when a plurality of TC terminals is connected to a TC server.
In the method of the above described Patent Document 1, each telephone terminal is identified while a plurality of softphones runs on a TC server in the TC system described above. Therefore, all communications between TC terminals and exterior IP phone terminals were communications via the TC terminal, and terminal-to-terminal communication that characterizes the fundamental operations of IP phones was not achieved. Furthermore, since the method required TC terminals to exist on the same network segment as the TC server, communications by TC terminals via the outside or wireless LANs were also not achieved.